Problem: $\dfrac{1}{4} + \dfrac{3}{5} = {?}$
Answer: ${\dfrac{1}{4}}$ ${\dfrac{3}{5}}$ $+$ ${\dfrac{1 \times 5}{4 \times 5}}$ ${\dfrac{3 \times 4}{5 \times 4}}$ $+$ ${\dfrac{5}{20}}$ ${\dfrac{12}{20}}$ $+$ $ = \dfrac{{5} + {12}}{20} $ $ = \dfrac{17}{20}$